Bengt H. Fellenius, Dr.Tech., P.Eng.2475 Rothesay Avenue, Sidney, British Columbia, V8L 2B9

TEL: (778) 426-0775 e-address: Web site: [www.Fellenius.net]

Basics of Design of Piled FoundationsA Course and Seminar

Santa Cruz, BoliviaApril 25, 2013

The primary intent of the course is to demonstrate that deep foundation design is a good deal more thanfinding some value of capacity. The course aims to show what data one must pull together and presentprocesses of analysis and calculations necessary for a design of a specific project. Aspects of negativeskin friction and associated drag load and downdrag are emphasized.

The presentation includes both broad generalities and in-depth details. Aspects of where to installinstrumentation, perform a test, and analyze the test data are addressed. Settlement analysis is of vitalimportance to the design of piled foundations, and the course addresses principles of settlement analysisand provides some of the mechanics of calculating settlement. A few aspects are included ofconstruction aspects as well as of Limit States Design, LSD (Ultimate Limit States, ULS, andServiceability Limit States, SLS, by Canadian terminology and Load and Resistance Factor Design,LRFD, by US terminology).

To simplify following along the flow of the presentation and taking notes, hand-out course notes areprovided, consisting of black-and-white copies of all Power Points slides, six to a page. Full-size colorcopies of the slides are also available on my web site [www.Fellenius.net]. These can be downloadedfrom the link [/Bolivia]. Note, the link is hidden and has to be typed into the command line ("commandribbon").

The slides contain only a minimum of text. For a background and explanation to much of thepresentations, I refer you to my text book "Basics of Foundation Design" also available for downloadingfrom my web site (the file is called 313 The Red Book_Basics of Foundation Design.pdf. Afterdownloading, the book can be viewed and read on-screen or be printed (color or black & white) withoutany restriction. The book contains a list of references pertinent to the material presented in the course.Copies of the referenced papers where I am the author or co-author are available for downloading at myweb site (click on the link "Download Papers").

I will be glad to respond to any e-mail with a question you might wish to put to me.

Sidney April 2013

Bengt H. Fellenius

Basics of Design of Piled FoundationsA Course and Seminar

Bengt H. Fellenius, Dr.Tech., P.Eng.The course comprises four main lectures leading up to and presenting the essentials of the Unified Method of deepfoundations design for capacity, drag load, settlement, and downdrag for single piles, pile groups, and piledfoundations. The presentations are illustrated with case histories of testing and design analysis including how toevaluate strain-gage measurements from instrumented pile loading tests and to assess residual load. Settlementanalysis is of vital importance to the design of piled foundations, and the course addresses principles of settlementanalysis and how to calculate settlement of piles and piled foundations. Pertinent aspects of constructionprocedures and Load and Resistance Factor Design, LRFD are discussed.

08:00h Brief Background to Basic Principles Applicable to Piled Foundations

Stress distribution and interaction between adjacent foundations; Settlement analysis; Applications ofwick drains to piled foundations.

09:30h Coffee Break

09:45h Analysis of Load Transfer, Capacity, and Response to LoadLoad-movement response of foundations; Bearing capacity and load-transfer by beta, alpha, and lambdamethods, and by CPT and CPTu methods; Set-up and relaxation; Residual load; Results of predictionevents.

11:30h The Static Loading Test: Performance, Analysis, and Instrumentation

Methods of testing and basic interpretation of the results. How to analyze results from strain-gageinstrumented piles to arrive at resistance distribution along the pile shaft and the pile toe response.

12.00h LUNCH

13:00h The Static Loading Test: Resumed

Determining pile elastic modulus. The importance of residual load and how to include its effect in theanalysis. Principles of the bi-directional test (the O-cell test) and how to analyze the results of an O-celltest. Case histories of analyses on results of static loading tests on driven and bored piles.

14:30h Coffee Break

14:50h 4. Piles and Pile Groups Long-Term Behavior and how we know what we know; The Unified Design Method.

Important case histories presenting studies that demonstrated the actual long-term response of piles toload and observed settlement of piles and pile groups. The lessons learnt will be referenced to aspects ofdesign applying the Unified Method for Design of Piled Foundations considering Capacity, Drag Load,Settlement, and Downdrag for single piles, pile groups, and piled foundations.

1. Capacity (choice of factor of safety, and rules of LRFD and Limit States Design) and design forstructural strength (including drag load)

2. Settlement of single piles and pile groups due to load directly on the piles and due to influence fromadjacent activity (downdrag)

3. How to combine the various aspects for the design of an actual case with emphasis on foundationsettlement illustrated with examples

17:00h Questions and Discussions; End of Day

1BASICS OF DESIGN OF PILED

FOUNDATIONSFOUNDATIONS

Bengt H. Fellenius

1

A short course

Santa Cruz, Bolivia, April 25, 2013

08:00h Brief Background to Basic PrinciplesApplicable to Piled Foundations

SCHEDULE

09:30h Break

09:45h Analysis of Load Transfer, Capacity and Response to Load

11.30h The Static Loading Test: Head-down and O-cell Tests

12.00h LUNCH

13.00h The Static Loading Test: Continued

14 00h Case Histories on Pile Analysis Drag Load Downdrag

2

14.00h Case Histories on Pile Analysis, Drag Load, Downdrag,Pile Groups, Piled Raft, Piled Pad

14.30h Break

14.50h The Unified Method of Design

17:00h Questions and Discussions and End of Day

2www.Fellenius.net

Bolivia

To Download All COURSE SLIDES

Power Point Slides1 - Background Lecture 1.pdf2 - Analysis Methods Lecture 2.pdf3 - Static Loading Test Lectures 3a and 3b.pdf4 - Case Histories and Lectures 4a and 4b.pdf

Design Methods

4

3/24/2013

1

BASICS OF DESIGN OF PILED

FOUNDATIONS

Bengt H FelleniusBengt H. Fellenius

Background and Basic Principles

Bolivia, April 25, 2013

Some Fundamental Principles

22

Determining the effective stress is the key to geotechnical analysis

The not-so-good method:

h= '' = buoyant unit weight

33

)'(' hz = )1(' iwt =

It is much better to determine, separately, the total stress and the pore pressure. The effective stress is then the total stress minus the pore pressure.

)( h

44

)( hz = uz = '

Determining pore pressure

u = w hThe height of the column of water (h; the head representing the water pressure)is usually not the distance to the ground surface nor, even, the distance to thegroundwater table. For this reason, the height is usually referred to as thephreatic height or the piezometric height to separate it from the depth below

PRESSURE

55

the groundwater table or depth below the ground surface.

The pore pressure distribution is determined by applying the facts that

(1) in stationary conditions, the pore pressure distribution can be assumed to be linear in each individual soil layer

(2) in pervious soil layers that are sandwiched between less pervious layers, the pore pressure is hydrostatic (that is, the vertical gradient is unity)

SAND Hydrostatic distribution

CLAY Non-hydrostatic distribution, but linear

SAND Hydrostatic distribution Artesian phreatic head

GW

DEPTH

Distribution of stress below a a small load area

0LBqqz

=

The 2:1 method

66

)()(0 zLzBqqz ++

The 2:1-method can only be used for distributions directly under the centerof the footprint of the loaded area. It cannot be used to combine (add)stresses from adjacent load areas unless they all have the same center. it isthen only applicable under the area with the smallest footprint.

3/24/2013

2

The Boussinesq Method Derived from calculation of stress from

a point load on the surface of an elastic medium

33z

77

2/522 )(23

zrzQqz +=

Newmarks method for stress from a loaded area

Newmark (1935) integrated the Boussinesq equation over a finite area and obtained a relation for the stress under the corner of a uniformly loaded rectangular area, for example, a footing

CBAI +

88

40CIqqz ==

2222

22

112nmnm

nmmnA +++++=

12

22

22

++++=

nmnmB

++++= 2222

22

112arctannmnm

nmmnC

m = x/zn = y/zx = length of the loaded areay = width of the loaded areaz = depth to the point under the corner

where the stress is calculated

(1)

Eq. 1 does not result in correct stress values near the ground surface. To represent the stress near the ground surface, Newmarks integration applies an additional equation:

CBA +

99

40CBAIqqz

+==

For where: m2 + n2 + 1 m2 n2

(2)

Stress distribution below the center of a square 3 m wide footing

-2

0

) 0 15

0.20

0.25

CTO

R,

IEq. (1)

Eq. (2) Eq. (2)

1010

0 20 40 60 80 100-6

-4

STRESS (KPa)

DE

PTH

(m

0.01 0.10 1.00 10.000.00

0.05

0.10

0.15

m and n (m = n)

INFL

UE

NC

E F

AC

Eq. (1)

0

1

2

0 25 50 75 100

STRESS (%)

met

ers)

Boussinesq

Westergaard

0

1

2

0 25 50 75 100

SETTLEMENT (%)

met

ers)

Boussinesq

Westergaard

1111Comparison between Boussinesq, Westergaard, and 2:1 distributions

3

4

5

DEP

TH (

dia

2:13

4

5

DEP

TH (

dia

2:1

0

1

2

0 25 50 75 100

STRESS (%)

eter

s)

Westergaard

Boussinesq

0

1

2

0 25 50 75 100

SETTLEMENT (%)

met

ers)

Boussinesq

Westergaard

1212

2

3

4

5

DEP

TH (

diam

2:1

2

3

4

5

DEP

TH (

diam

2:1

3/24/2013

3

0

1

2

0 25 50 75 100

STRESS (%)

amet

ers)

Westergaard

Boussinesq

0

1

2

0 25 50 75 100

SETTLEMENT (%)

amet

ers)

Boussinesq

Westergaard

1313

3

4

5

DE

PTH

(di

a

2:1 Characteristic Point; 0.37b from center

3

4

5

DEP

TH (

dia

2:1 Characteristic Point; 0.37b from center

Below the characteristic point, stresses for flexible and stiff footings are equal

Now, if the settlement distributions are so similar, why would we persist in using

Boussinesq stress distribution instead of the much simpler 2:1 distribution?

1414

Because a footing is not alone in this world; near by, there are other footings, and fills,

and excavation, etc., for example:

The settlement imposed outside the loaded

foundation is often critical

0

1

2

0 25 50 75 100

SETTLEMENT (%)

met

ers)

BoussinesqOutside Point Boussinesq

Center Point

1515

2

3

4

5

DEP

TH (

diam

Loaded area

The end result of a geotechnical design analysis

is

1616

Settlement

Stress-Strain

' (

KPa

)

=tM

1717

STRAIN (%)

STR

ESS,

Plotted as Strain-Stress

N (

%)

N (

%)

TIO

, e

Plotted as Void Ratio vs. Stress

1818

STRESS, ' (KPa)

STR

AIN

STRESS, ' (KPa)

STR

AIN

STRESS (KPa)

VOID

RA

T

3/24/2013

4

Stress-strain behavior is non-linear for most soils. The non-linearity cannot be disregarded when analyzing compressible soils, such as silts and clays, that is, the elastic modulus approach is not appropriate for these soils.

Non-linear stress-strain behavior of compressible soils, is conventionally modeled as follows.

11 'l'l C

1919

where = strain induced by increase of effective stress from 0 to 1Cc = compression indexe0 = void ratio0 = original (or initial) effective stress1 = final effective stressCR = Compression Ratio = (MIT)

0

1

0

1

0 'lg

'lg

1

CR

eCc =+=

01 eCCR c+=

Some use the term "Cc" for the "CR", creating quite a bit of confusion thereby

In overconsolidated soils (most soils are)

)''lg

''

lg(1

1 100 p

cp

cr CCe

++=

2020

where p = preconsolidation stressCcr = re-compression index

The Janbu Method

The Janbu tangent modulus approach, proposed by Janbu (1963; 1965; 1967; 1998), and referenced by the Canadian Foundation Engineering Manual, CFEM (1985; 1992), applies the same basic principles of linear and non-linear stress-strain behavior. The method applies to all soils, clays as well as sand. By this method, the relation between stress and strain is a function of two non-dimensional parameters which are unique for a soil: a stress exponent, j, and a modulus number, m.

2121

Janbus general relation is

])''()

''[(1 01 j

r

j

rmj

=

where: r = a reference stress = 100 KPaj = a stress exponent

m = the modulus number

The Janbu Method

Dense Coarse-Grained Soil j = 1

Cohesive Soil j = 0 1'

ln1 =

'1)''(1 01 == mm

'21)''(

21

01 == mm

in KPa

in ksf

2222

Cohesive Soil j = 0

Sandy or Silty Soils j = 0.5

0'ln m=

)''(51

01 = m

pm''(2 1 =

in KPa

in ksf

There are direct mathematical conversions

between m and the E and Cc-e0

For E given in units of KPa (and ksf), the relation between the modulus number and the E-modulus is

2323

m = E/100 (KPa)m = E/2 (ksf)

For Cc-e0, the relation to the modulus number is

cc Ce

Cem 00 13.2110ln +=+= And m = 2.3/CR

Typical and Normally Conservative Modulus Numbers

SOIL TYPE MODULUS NUMBER STRESS EXP.

Till, very dense to dense 1,000 300 (j=1)

Gravel 400 40 (j=0.5)

Sand dense 400 250 (j=0.5compact 250 150 _ " _loose 150 100 _ " _

Silt dense 200 80 (j=0.5)compact 80 60 _ " _loose 60 40 _ " _

This is where the greater value of the Janbu approach versus the MIT CR-approach comes in.

ClaysSilty clay hard, stiff 60 20 (j=0)

stiff, firm 20 10 _ " _Clayey silt soft 10 5 _ " _

Soft marine claysand organic clays 20 5 (j=0)

Peat 5 1 (j=0)

For clays and silts, the recompression modulus, mr, is often five to twelve times greater than the virgin modulus, m.

This is where the Janbu approach and the MIT CR-approach are equal in practicality.

Reference: Fellenius, B.H., 2012. Basics of foundation design, a text book.Revised Electronic Edition, [www.Fellenius.net], 385 p.

3/24/2013

5

0.80

1.00

1.20

Voi

d R

atio

(- -

)

m = 12(CR = 0 18)

p'c

10

15

20

25

Stra

in (

%)

C

1/m

Slope = m = 12

Evaluation of compressibility from oedometer results

2525

0.40

0.60

10 100 1,000 10,000

Stress (KPa) log scale

V (CR = 0.18)

0

5

10 100 1,000 10,000

Stress (KPa) log scale

p 10p

Cc

Cc = 0.37

e0 = 1.01 p'c

p 2.718p

Void-Ratio vs. Stress and Strain vs. Stress Same test data

Note, if the "zero"-value -- the e0 -- is off, the Cc-e0 is off (and so is the CR) even ifthe Cc is correctly determined. Not so the "m" (if determined from the test results).

Comparison between the Cc/e0 approachand the Janbu method

0 10

0.15

0.20

0.25

0.30

0.35

PRES

SIO

N IN

DEX

, Cc

Do these values indicate a

compressible soil, a medium compressible

soil, a moderately ibl il

15

20

25

30

35

MO

DU

LUS

NU

MB

ER, m

2626

Data from a 20 m thick sedimentary deposit

0.00

0.05

0.10

0.40 0.60 0.80 1.00 1.20

VOID RATIO, e0

CO

MP compressible soil, or a

non-compressible soil?0

5

10

0.400.600.801.001.20

VOID RATIO, e0

VIR

GIN

The Cc-e0 approach (based on Cc) implies that the compressibility varies by 30 %.

However, the Janbu methods shows it to vary only by 10 %. The modulus number, m, ranges from 18 through 22; It would be unusual to find a clay with less variation.

Conventional Cc/e0

How many of these oedometer results indicate

(o) highly compressible clay

(o) compressible clay

( ) di ibl l20

30

40

50

OD

ULUS

NU

MB

ER, m

0 20 40 60 80 100WATER CONTENT, wn (%)

Janbu Modulus Number m

The Cc-values converted via the associated e0-values to modulus

numbers.

2

3

4

5

MPR

ESSI

ON

IND

EX, C

c

2727

(o) medium compressible clay

(o) non-compressible clay?

0

10

0.00 0.50 1.00 1.50 2.00 2.50 3.00

VOID RATIO, e0

VIRG

IN M

m < 10 ==> Highly compressible Oedometer test data from Leroueil et al., 1983

0

1

0.00 1.00 2.00 3.00

VOID RATIO, e0

CO

M

Stress produces strainLinear Elastic Deformation (Hookes Law)

= induced strain in a soil layer= imposed change of effective stress in the soil layer '

E' =

2828

p g y

E = elastic modulus of the soil layer (Youngs Modulus)

Youngs modulus is the modulus for when lateral expansion is allowed, which may be the case for soil loaded by a small footing, but not when the load is applied over a large area. In the latter case, the lateral expansion is constrained (or confined). The constrained modulus, D, is larger than the E-modulus. The constrained modulus is also called the oedometer modulus. For ideally elastic soils, the ratio between D and E is:

= Poissons ratio

)21()1()1(

+

=ED

Settlement is due to Immediate Compression, Consolidation Settlement, and Secondary Compression

Immediate Compression is the compression of the soil grains (soil skeleton) and of any free gaspresent in the voids. It is usually assumed to be linearly proportional to the change of stress Theimmediate compression is therefore often called 'elastic' compression. It occurs quickly and isnormally small (it is not associated with expulsion of water).

Consolidation (also Primary Consolidation) is volume reduction during the increase ineffective stress occurring from the dissipation of pore pressures (expelling water from the soilbody). In the process, the imposed stress, initially carried by the pore water, is transferred to the

il t t C lid ti i kl i i d il b t l l i fi i d

2929

soil structure. Consolidation occurs quickly in coarse-grained soils, but slowly in fine-grainedsoils.

Secondary Compression is a term for compression occurring without an increase of effectivestress. It is triggered by changes of effective stress. It does not usually involve expulsion ofwater, but is mainly associated with slow long-term compression of the soil skeleton. Somecompression of the soil structure occurs and it is then associated with some expulsion of water,but this is so gradual and small that pore pressure change is too small to be noticed. Sometimes,the term "creep" is used to mean secondary compression, but "creep" should be restricted toconditions of shear. Secondary compression is usually small, approximately similar in magnitudeto the immediate compression, but may over time add significantly to the total deformation of thesoil over time. Secondary compression can be very large in highly organic soils, such as peat.Theoretically, seconday compression occurs from the start of the consolidation (effective stresschange), but in practice, it is considered as starting at the end of the consolidation.

On applying load, the soil skeleton compresses and the soil grainsare forced closer to each other reducing the void ratio. Thecompression of the soil skeleton occurs more or less immediately incontrast to the reduction of the void volume which requiresexpulsion of water ("consolidation") and can take a long time.However, in soils containing gas bubbles, the load applicationcauses the bubbles to compress (and partially to go into solution in

Immediate Compression and Consolidation Settlement

3030

the pore water), which also occurs immediately. Then, as the porepressure dissipates during the consolidation process, the gasbubbles expand which slows down the settlement process. The"slow-down" is often mistaken for approaching the end ofconsolidation. The thereafter observed settlement is theninterpreted as a large secondary compression (addressed later on).

3/24/2013

6

2H

Drainage Layer

Clay Layer (consolidating)

Drainage Layer

0

1uu

SSU t

f

tAVG ==

where UAVG = average degree of consolidation (U)St = settlement at Time tSf = final settlement at full consolidationut = average pore pressure at Time tu0 = initial average pore pressure (on application of the load at Time t = 0)

Basic Relations

UAVG

Consolidation Settlement

3131

vv c

HTt2

=where t = time to obtain a certain degree of consolidation

Tv = a dimensionless time coefficient: cv = coefficient of consolidationH = length of the longest drainage path

UAVG (%) 25 50 70 80 90 100

Tv 0.05 0.20 0.40 0.57 0.85 1.00

)1(lg1.0 UTv =

HOW TO HANDLE A MULTILAYERED PROFILE?

c/c

d

"Square" spacing: D = 4/ c/c = 1.13 c/c

"Triangular" spacing: D = (23)/ c/c = 1.05 c/c

Vertical Drains

3232

c/cBasic principle of consolidation process in the presence of vertical drains

hh Ud

DT = 11ln]75.0[ln

81

hh UdD

cDt = 1

1ln]75.0[ln8

2

and

hh c

DTt2

=

The Kjellman-Barron Formula

Walter Kjellman, inventor of the very first wick drain, the Kjellman Wick, a 100 mm wide, 3 mm thick, cardboard drain that became the prototype for

33

p ypall subsequent wick drains.

Walter Kjellman, 1950

Important Points

Build-up of Back Pressure

The consolidation process can be halted if back-pressure is let to build-up below the embankment, falsely implying that the process is completed

3434

Flow in a soil containing pervious lenses, bands, or layers Theoretically, vertical drains operate by facilitating horizontal drainage. However, where pervious lenses and/or horizontal seams or bands exist, the water will drain vertically to the pervious soil and then to the drain. When this is at hand, the drain spacing can be increased significantly.

Pervious seams (silt or sand) will dry faster than the main body of clay. The pervious seams can be observed in a Shelby sample during the drying process, as indicated in the photos.

3535

p

CPTU soundings with readings every 10 mm can also disclose the presence of sand and silt seams (if they are thicker than about 10 mm; which the illustrated small seams are not).

How deep do the wick drains have to be installed?

In theory, the drains do not need to go deeper than to where the applied stress is equal to the preconsolidation stress.

However in practice it is a good rule to always go down to a

3636

However, in practice, it is a good rule to always go down to a pervious soil layer (aquifer) to ensure downward drainage. But, if the surcharge is by vacuum treatment or combined with vacuum treatment, it is better to avoid having the drains in an aquifer, or they would "suck".

3/24/2013

7

3737

The Kjellman wick, 1942 The Geodrain, 1972

3838

The Geodrain, 1976

Wick drain types

The Burcan Drain, 1978

The Mebra Drain 1984 (a development of the

Castleboard Drain 1979)

3939

0

5

10

15

20

25

30

35

40

0 100 200 300Pore Pressure (KPa)

Dep

th (

m)

Wick Drains Installed

m)

Settlement at center of a 3.6 m high embankment BangkokAirport. Wick drains at c/c 1.5 m were installed to 10 m depth.

PORE PRESSUREEnlarged

40

AVERAGE MEASURED SETTLEMENT

DESIGN CURVE FOR THISSURCHARGE (75 KPa)

1.0 m

FINAL HEIGHTOF FILL

SET

TLEM

ENT

(mm

)

200 days

FILL

HEI

GH

T (m

CalculatedTotalSettlements

Settlement and Horizontal Displacement for the 3.6 m Embankment

WICK DRAINS TO 10 m DEPTHWICK DRAINS TO 10 m DEPTH

Settlement was monitored in center and at embankment sides and horizontal displacement was monitored near sides of embankment

Note the steep slopes

4141

Time from start to end of surcharge placement = 9 monthsObservation time after end of surcharge placement = 11 months

1.0 m

2.0 m

WICK DRAIN

Moh and Lin 2006

Horizontal Displacement versus Settlement at Different Test Locations

OVE

MEN

T (c

m)

4242

HOR

IZO

NTA

L M

O

SETTLEMENT (cm)

3/24/2013

8

Secondary Compression

1000

log1 t

te

C +=The value of the Coefficient of Secondary Compression, C, is usually expressed as aratio to the consolidation coefficient, Cc, ranging from 0.02 through 0.07 with an averageof about 0.05 (Holtz and Kovacs 1981). For example, in a soft clay with Cc of about 0.3

d f b t it (i d l b f 15) C ld b b t 0 01

4343

and e0 of about unity (i.e., a modulus number of 15), C, would be about 0.01.

The key parameter, however, it the t100 value, the time it takes for 100 % of consolidation (or 90 %, more realistically) to develop. Also when using wick drains, the 100-% should be the time for vertical drainage, not horizontal.

It is commonly assumed that secondary compression does not start until primary consolidation is completed; U = 100 %. However, the consensus amongst the experts is that secondary compression starts as soon as a change of effective stress has been triggered, i.e., it starts at at 0 % consolidation.

The purpose of calculating stresses is to calculate settlement. The following showssettlements calculated from the Boussinesq distribution. how stress applied to thesoil from one building affect the settlement of an adjacent existing 'identical'building loaded the same constructed about 5 years before.

EXISTING ADJACENT BUILDING

NEW BUILDING

WITH SAME LOAD OVER FOOTPRINT

AREA

The 2nd building was constructed five years after the 1st building. The 1st building had then settled about 80 mm (3 inches), which was OK albeit close to what was felt to be

4444The soils consist of preconsolidated (OCR = 2) compressible silt and clay

6.5 m6.5 m 4 m m

1st Building

2nd Building

was OK, albeit close to what was felt to be acceptable. Did the construction of the 2nd building add settlement to the 1st, and what was the settlement of the 2nd building?

(Because the buildings are on raft foundation, the characteristic point is the most representative point for the settlement calculations).

The settlement of the first building calculated using UniSettle Version 4

0 2 4 6 8 10YEARS

SETTLEMENT OVER TIME

4545

020406080

100120

0 2 4 6 8 10

SETT

LEM

ENT

(mm

)

2nd Building constructed

Calculations using Boussinesq distribution can be used to determine how stressapplied to the soil from one building may affect an adjacent existing building(having the same loading as the new building).

0

5

0 20 40 60 80 100

STRESS (%)

STRESSES UNDER AREA

BETWEEN THE TWO BUILDINGS

EXISTING ADJACENT BUILDING

NEW BUILDING

WITH SAME LOAD OVER FOOTPRINT

AREA

4646

10

15

20

25

30

DEP

TH (

m)

STRESSES ADDED TO THOSE UNDER THE FOOTPRINT OF THE ADJACENT BUILDING

STRESSES UNDER THE FOOTPRINT OT THE LOADED BUILDING

TWO BUILDINGS

Calculations by means of UniSettleThe soils consist of preconsolidated

moderately compressible silt and clay

6.5 m6.5 m 4 m m

Calculations using Boussinesq stress distribution can be used to determine howstress applied to the soil from one building may affect an adjacent existing building(having the same loading as the new building).

EXISTING ADJACENT BUILDING

NEW BUILDING

WITH SAME LOAD OVER FOOTPRINT

AREA

0

5

10

0 20 40 60 80 100

STRESS (%)

STRESSES UNDER THE AREA

BETWEEN THE TWO BUILDINGS

PRECONSOLIDATION MARGIN (Reducingwith depth)

4747The soils consist of preconsolidated moderately compressible silt and clay. The preconsolidation margin reduces with depth.

6.5 m6.5 m 4 m m

10

15

20

25

30

DEP

TH (

m)

CENTER STRESSES COMBINED

STRESSES UNDER THE FOOTPRINT OF THE LOADED BUILDING

STRESSES FROM LOADED BUILDING CALCULATED UNDER THE FOOTPRINT OF THE ADJACENT BUILDING

Settlement distributions (UniSettle Version 4)

0

5

10

0 20 40 60 80 100 120

SETTLEMENT (mm)

1st ONLY

Increase due to 2nd Bldng BOTHSand &

Gravel

Silty Clay

0

5

10

0 20 40 60 80 100 120

SETTLEMENT (mm)

Of ground due to 1st Bldng only

Due to 2nd Bldng

4848

15

20

25

30

35

DEP

TH (

m)

1st BUILDING

Soft Clay 15

20

25

30

35

DEP

TH (

m)

2nd BUILDING

3/24/2013

9

-83 KPa

105 KPa

34 KPa

85 KPa

105 + 34 + 85 = 224 - 83 141 KPa

110 m

38 m74 m

MORE ON SETTLEMENT

YEARYEAR

49

Briaud et al. 2007; Fellenius and Ochoa 2008

0

50

100

150

200

250

300

350

4001936 1946 1956 1966 1976 1986 1996 2006

YEAR

SETT

LEM

ENT

(m

m)

.

0

50

100

150

200

250

300

350

400

1 10 100

SETT

LEM

ENT

(mm

)

1936 1937 1940 1945 1950 1960 1975 2000

LINEAR PLOTLOWER SCALE

LOGARITHMIC PLOTUPPER SCALE

1936 1946 1956 1966 1976 1986 1996 2006

0

20

40

60

80

100

120

140

YEAR

WA

TER

DEP

TH (

m)

132a- 14m217 - 26m216a- 39m115 -153m209 -159m111 -161m501a-180m912 -206m114a-261m618 -267m606 -301m501b-365m132b-442m114b-480m

1925 1935 1945 1955 1965 1975 1985 1995 2005 2015

SHALLOW WELLS

DEEP WELLS

Water Depths Measured in Deep Wells

50

Monument and Well Locations

Well head at Burnett School, Baytown, Texas

YEAR

51

0

50

100

150

200

250

300

350

400

1 10 100

YEAR

SE

TTLE

ME

NT

(mm

)

1936 1937 1940 1945 1950 1960 1975 2000

DEPTH TO WATER TABLE

SETTLEMENT

0

25

50

75

100

125

DEP

TH T

O W

ATE

R T

AB

LE (

m)

San Jacinto MonumentSettlement and Measured Depths to Water in the Wells Plotted Together

1925

The lowering of the pore pressures due to mining of water and subsequent regionalsettlement is not unique for Texas. Another such area is Mexico City, for example.Here is a spectacular 1977 photo from San Joaquin, California.

52

1977

1955

Subsidence at San Joaqu in Valley, California

0.0

0.5

1.0

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

YEAR

ent

(m)

I II III IV

5353

1.5

2.0

2.5

Settl

eme

NEW ORLEANS 1924 - 1978

I. Initial Period of Pumping II. Increased Pumping III. Further Increased IV. Reduced Pumping

Data from Kolb, C.R. and Saucier, RT., 1982

Site Investigation Techniques

The SPT and the CPT/CPTu

3/24/2013

10

The SPTExample from Atlantic coast of South USA

0

5

10

15

0 20 40 60 80 100

SPT N-Indices (bl/0.3m)

0

5

0 10 20 30 40 50

SPT N-Indices (bl/0.3m)

5555

20

25

30

35

40

45

50

DEP

TH (

m)

East Abutment

10

15

20

25

DEP

TH (

m)

DETAIL

0

10

20

30

40

0 20 40 60 80 100

N-Index (bl/0.3m)

H (

m)

0

10

20

30

40

0 20 40 60 80 100

N-Index (bl/0.3m)

H (

m)

0

10

20

30

40

0 20 40 60 80 100

N-Index (bl/0.3m)

H (

m)

Example from Atlantic coast of

Canada

5656

40

50

60

70

80

DE

PT 40

50

60

70

80

DE

PT 40

50

60

70

80

DE

PT

SPT for design After problems arose

Forensics

0

10

20

30

0 20 40 60 80 100

N-Index (bl/0.3m)

m)

With all data points

5757

30

40

50

60

70

80

DE

PTH

(m

0.010

0.100

1.000

mv (

1/M

Pa)

30405060708090

100

Mod

ulus

(M

Pa)

Direct numerical use of the SPT N-index

5858

0.0011 10 100

N60-Index (bl/0.3m)

01020

0 10 20 30 40 50N60-Index (bl/0.3m)

(after Terzaghi, Peck, and Mesri 1996 from Burland and Burbidge 1985)

Determining pile Capacity from SPT-indices

0

5

10

15

0 10 20 30 40

SPT N-Index (bl/0.3m)

(m)

0

5

10

15

0 10 20 30 40

SPT N-Index (bl/0.3m)

(m)

0

5

10

15

0 10 20 30 40Cone Stress, qt (MPa)

(m)

5959

20

25

30

35

DEP

TH (

Estimated required depth

20

25

30

35

DEP

TH (

Potentially possible depth

Estimated required depth1

2

Pile 1 had a much smaller capacity than Pile 2!

20

25

30

35

DEP

TH (

N (bl/ft)

Pile 1 had a much smaller capacity than Pile 2!

2

1

Principles of the CPT and CPTU

The Cone Penetrometer

606060

Sleeve friction, fs

Pore PressureU2 position

Cone Stress, qc

U2 Position = pore pressure measured on the cone shouldercone shoulder

3/24/2013

11

616161 626262

6363 6464

Continuous cores samples obtained by pushing down a pipe having an inside plastic tube. On withdrawal and cutting the tube open, the soil sample is available in a better condition than a sample in a SPT-spoon.

Courtesy of Pinter and Associates, Saskatoon, SK.

0

10

0 10 20 30

INCLINATION ANGLE ()

(m)

0

10

0 2 4 6 8

RADIAL DEVIATION (m)

(m)

0

10

0.0 0.3 0.5 0.8 1.0

DEPTH DEVIATION (m)

(m)

The CPT sounding rod is never truly vertical, of course.

How much can it be off?

6565

20

30

40

50

AC

TUA

L D

EPTH

20

30

40

50

AC

TUA

L D

EPTH

20

30

40

50

AC

TUA

L D

EPTH

5

10

15

20

25

Y-D

irect

ion

(m)

20.6 m

PLAN VIEW

"Unfolded"

0

10

20

30

40

50

0 1 2 3 4

DEPTH DEVIATION (m)

EPTH

(m

)

0

10

20

30

40

50

0 5 10 15 20 25

RADIAL DEVIATION (m)

EPTH

(m

)

6666

-5

0

-5 0 5 10 15 20 25

X-Direction (m)

Example 2

60

70

80

90

100

DE

60

70

80

90

100

DE

Inclination plane

X-plane Y-plane

3/24/2013

12

0

5

10

15

0 10 20 30Cone Stress, qt (MPa)

TH (

m)

0

5

10

15

0 100 200

Sleeve Friction (KPa)TH

(m

)

0

5

10

15

0 100 200 300 400

Pore Pressure (KPa)

TH (

m)

0

5

10

15

0.0 1.0 2.0 3.0 4.0

Friction Ratio (%)

TH (

m)

CLAY CLAYCLAY

6767

20

25

30

DEP

T 15

20

25

30

DEP

T 15

20

25

30

DEP

T

20

25

30

DEP

T

SILT SILT SILT

SAND SAND SAND

Results of a CPTU sounding

Soil profilingApplications

6868The Begemann original profiling chart (Begemann, 1965)

1

10

100

Con

e St

ress

, qt

(MPa

)

4

56

7

8

9

10

11

12

Friction Ratio from 0.1 % through 25 %

6969

Profiling chart per Robertson et al. (1986)

01 10 100 1,000

Sleeve Friction (KPa)

C

12

3 25 %

7070Profiling chart per Robertson (1990)

1

10

100

Con

e St

ress

, qE

(MPa

) 5 1 = Very Soft Clays, or Sensitive or Collapsible Soils 2 = Clay and/or Silt 3 = Clayey Silt and/or Silty Clay 4a = Sandy Silt 4b = Silty Sand 5 = Sand to Sandy Gravel

3

4

7171

0.11 10 100 1,000

Sleeve Friction (KPa)

1 2

The Eslami-Fellenius profiling chart (Eslami 1996; Eslami and Fellenius, 1997)

Example of a CPTU sounding from a river estuary delta (Nakdong River, Pusan, Korea)

0

10

20

30

0 10 20 30Cone Stress, qt (MPa)

DEP

TH (

m)

0

10

20

30

0 200 400

Sleeve Friction (KPa)

DEP

TH (

m)

0

10

20

30

0 250 500 750 1,000

Pore Pressure (KPa)

DEP

TH (

m)

0

10

20

30

0 1 2 3 4 5

Friction Ratio (%)

DEP

TH (

m)

Profile

Mixed

CLAY

7272

The sand layer between 6 m and 8 m depth is potentially liquefiable.The clay layer is very soft.

The sand below 34 m depth is very dense and dilative, i.e., overconsolidated and providing sudden large penetration resistance to driven piles and relaxation problems.

30

40

50

30

40

50

30

40

50

30

40

50

SAN

Reduced pore pressure (dilation)

SAND

3/24/2013

13

1

10

100

one

Stre

ss, q

E (M

Pa)

5

3

4

7373

0.11 10 100 1,000

Sleeve Friction (KPa)

Co

1 2

The CPTU data of the Preceding Slide plotted in an Eslami-Fellenius Chart

The CPTU is an excellent and reliable tool for soil identification, but there is more to geotechnical site

investigation than just establishing the soil type.

And, the CPTU can deliver much more than soil profiling

7474

Liquefaction7.4 Magnitude Earthquake of August 17, 1999

Kocaeli, Adapazari, Turkey

7575

Photos courtesy of Noel J. Gardner, Ottawa

7676

Photo courtesy of Noel J. Gardner, Ottawa

dv

v rg

aCSR 'max65.0

=CSR = Cyclic Stress Ratio

For earthquakemagnitude of 7.5

An earthquake generates a Cyclic Stress Ratio, CSR

Assessment of liquefaction risk fromresults of a CPTU sounding

7777

amax = maximum horizontal acceleration at ground surface (m/s2)

g = gravity constant (m/s2)

v = total overburden stress (Pa)

'v = effective overburden stress (Pa)

rd = stress reduction coefficient for depth (dimensionless)

z = depth below ground surface (m)

CRR

The safety against liquefaction depends on the Cyclic Resistance Ratio, CRR, determined from the CPTU data

7878

CSRCRRFs = For earthquake magnitude of 7.5

3/24/2013

14

KPaqforqCRR cc 5005.0100833.0 11

3/24/2013

15

0

1

2

3

4

5

0 5 10 15Cone Stress (MPa)

TH (

m)

0

1

2

3

4

5

0 10 20 30 40 50Sleeve Friction (KPa)

TH (

m)

0

1

2

3

4

5

0 50 100 150 200Pore Pressure (KPa)

TH (

m)

0

1

2

3

4

5

0.0 0.1 0.2 0.3 0.4 0.5Friction Ratio (%)

TH (

m)

7 Days7 Days

Before

8585

6

7

8

9

10

DE

PT

6

7

8

9

10

DE

P

6

7

8

9

10

DE

PT

6

7

8

9

10

DE

PT

7 DaysBeforeBefore

Geometric average values of cone stress, sleeve friction, and friction ratios andmeasured pore pressures from CPTU soundings at Chek Lap Kok Airport beforeand seven days after the vibratory compaction.

Fs versus depth0

1

2

3

4

5

0.00 1.00 2.00 3.00 4.00 5.00

Factor of Safety, Fs (--)

PTH

(m

)

Before Compaction

7 Days after

CSRCRRFs =

8686

Factor of safety against liquefaction before and after vibratory compaction

6

7

8

9

10

DEP compaction

CPT and CPTU Methods

for Calculating the Ultimate

Resistance (Capacity) of a Pile

Schmertmann and Nottingham (1975 and 1978)

8787

Meyerhof (1976)

deRuiter and Beringen (1979)

LCPC, Bustamante and Gianeselli (1982 )

Eslami and Fellenius (1997 )

ICP, Jardine, Chow, Overy, and Standing (2005)

But we will save those methods for later

Vibrations from Pile Driving

v = 433 EhZ P

M g hr

= 433 EhZ P

M g hx2 + z2

V = vertical component of the ground vibration, m/sEh = hammer efficiency coefficientZP il i d N /

88

ZP = pile impedance, Ns/mM = hammer (ram) mass, NG = acceleration, m/s2H = hammer height-of-fall, m, taken as the equivalent

height-of-fall that corresponds to the kinetic energyat impact

z = pile penetration depth, mx = horizontal distance at the ground surface from pile

to observation point, m

Most ground vibrations are generated from the pile toe

6

8

10

12

14

16

18

20

brationVelocity,

v0(m

m/s)

89

0

2

4

0 5 10 15 20 25 30 35 40 45 50

Distancetopiletoe,r(m)

Vi

Vibrations from driving a long toe bearing pile: measured compared to calculated

3/24/2013

1

BASICS OF DESIGN OF PILED

FOUNDATIONS

Bengt H Fellenius

1

Bengt H. Fellenius

Load Transfer and Capacity of Piles

Bolivia, April 25, 2013 22Driving closed-toe pipe piles into fine sand about 2.5 m above the groundwater table

33Driving 12-inch precast concrete pile into clay for Sidbec in 1974

Head measured in aquifer below the clay layer

44Svrta River 1969

GW

What really is Capacity?

For piles, capacity is

what we determine in

55

define from

a loading test

?

e.g.: The Offset Limit Load (Davisson, 1972)

Do you agree that this pointon the curve represents thecapacity of the pile?

Qu

Qu

66

Rs

Rt

3/24/2013

2

NbNqNcr qcu '5.0'' ++=and for Footings?

The Bearing Capacity Formula

where ru = ultimate unit resistance of the footingc = effective cohesion interceptB = footing width b d ff ti t t th f d ti l l

77

q = overburden effective stress at the foundation level = average effective unit weight of the soil below the foundation

Nc, Nq, N = non-dimensional bearing capacity factors

The main factor is the

Nq

Nq

88

Nq

But what is the reality?

Results of static loading tests on 0.25 m to 0.75 m square footings in well graded sand (Data from Ismael, 1985)

400

500

600

700

D

( KN

)

1.00 m

0.75 m

0.50 m

0.25 m

1,000

1,200

1,400

1,600

1,800

2,000

S S

( K

Pa

)

Normalized

99

0

100

200

300

0 10 20 30 40 50

SETTLEMENT (mm)

L O

A D

MOVEMENT

0

200

400

600

800

,

0 5 10 15 20

MOVEMENT/WIDTH (%)

S T

R E

S

1.00 m

0.75 m

0.50 m

0.25 m

Normalized

0

2

4

0 5 10 15 20Cone Stress, qt (MPa)

0

2

4

0 100 200 300 400

Sleeve Friction, fs (KPa)

0

2

4

0 20 40 60 80

Pore Pressure (KPa)

0

2

4

0 1 2 3 4 5

Friction Ratio, fR (%)

SAND

CPTU PROFILE

Load-Movement for Five Footings on Sandat Texas A&M University Experimental Site.

J-L. Briaud and R.M. Gibbens, 1994, ASCE GSP 41,

10

6

8

10

12

14

16

DEPT

H (

m)

6

8

10

12

14

16

DEPT

H (m

)

6

8

10

12

14

16

DEP

TH (

m)

6

8

10

12

14

16

DEPT

H (m

)

SANDY CLAYEY SILT

Eslami- RobertsonFellenius

As before the data will tell usmore, if we divide the load withthe footing area (to get stress)and divide the movement withthe footing width, as follows.

Load-Movement of Four Footings on SandTexas A&M University Experimental Site

ASCE GSP 41, J-L Briaud and R.M. Gibbens 1994

8,000

10,000

12,000

N )

3.0 m

3.0 m 1,400

1,600

1,800

2,000

KPa

)

Texas A&MSettlement Prediction Seminar

11

0

2,000

4,000

6,000

,

0 50 100 150 200

MOVEMENT ( mm )

L O

A D

(

KN

1.5 m

1.0 m

2.5 m

0

200

400

600

800

1,000

1,200

0 5 10 15 20

MOVEMENT / WIDTH (%)

S T

R E

S S

(

Load-Movement of Four Footings on SandTexas A&M University Experimental Site

ASCE GSP 41, J-L Briaud and R.M. Gibbens 1994

8,000

10,000

12,000

N )

3.0 m

3.0 m1,600

2,000

)

e

QQ

=

2

1

2

1

e = 0.4

q-z curve:

We can also borrow from pileanalysis (Pile toe response) andapply a q-z function to the stress-movement data. The "Ratio" functionis applied here.

Texas A&MSettlement Prediction Seminar

12

0

2,000

4,000

6,000

,

0 50 100 150 200

MOVEMENT ( mm )

L O

A D

(

KN

1.5 m

1.0 m

2.5 m

0

400

800

1,200

0 5 10 15 20MOVEMENT/WIDTH, (%)

STR

ESS,

(KPa

)

3/24/2013

3

Lehane et al. 2008Settlement Prediction Seminar

200

250

300

350

400

450

500

OA

D (

KN

)

1.0 m 1.5 m

1.0 m

200

300

400

500

RES

S (K

Pa)

1.0 m

13

Lehane, B.M., Doherty, J.P., and Schneider, J.A., 2008. Settlement prediction for footings on sand. Conference on Deformational Characteristics of Geomaterials. S.E. Burns, P.W. Mayne, and J.C. Santamarina (Editors), Atlanta, September 22-24, 2008, Vol. 1, pp.133-150.

0

50

100

150

0 10 20 30 40 50

MOVEMENT (mm)

L

0

100

0 1 2 3 4 5 6 7 8

MOVEMENT / WIDTH (%)

STR

Footing, 1.5 mFooting 1.0 mFooting 1.0 m

Six footings on gravel

Caisson under air pressure to control water level.

GW//\\//\\//\//\\//\\ //\\//\\//\//\\//\\

14 m16 m

6,000

8,000

10,000

12,000

14,000

TRES

S (K

Pa)

0.3 x 0.3

14Kusakabe, O., Maeda, Y., and Ohuchi, M., 1992. Large-scale loading tests of shallow footings in pneumatic caisson. ASCE Journal of Geotechnical Engineering, 118(11) 1681-1695.

"SCORIA" = Sandy GRAVEL, trace fines. An "interlocked" and highly overconsolidated volcanic soil.

e0 = 1.2, wn = 40 %, = 1,800 kg/m3

``W

Footing test

!?

0

2,000

4,000

0 5 10 15 20 25 30 35 40

NORMALIZED MOVEMENT (%)

ST

0.3 x 0.30.4 x 0.40.7 X 0.71.3 X 1.30.4 X 1.20.4 X 2.0

8,000

10,000

12,000

14,000

ESS

(KPa

)

Considering the "Preloading"/"Reloading"/"Prestress" Effect

15

0

2,000

4,000

6,000

0 5 10 15 20 25 30 35 40

NORMALIZED MOVEMENT (%)

STR

E

0.3 x 0.30.4 x 0.40.7 X 0.71.3 X 1.30.4 X 1.20.4 X 2.0

Data from Kusabe et al. 1992

Plate loading tests on 0.55 m x 0.65 m and 1.10 m x 1.30 m rectangular slabs in silty sand at Kolbyttemon, Sweden

1,500

2,000

(KPa

)

TREND1 1m x 1 3m

16Fellenius (2011). Data from Bergdahl, U., Hult, G., and Ottosson, E. (1984)

0

500

1,000

0 1 2 3 4 5 6 7 8 9 10MOVEMENT (%)

STR

ESS

0.55m x 0.65m

1.1m x 1.3m

Ultimate Shaft Resistance

rs, RsUltimate Shaft Resistance

is a reality

1717

Ultimate Toe Resistance does not exist other than as a definition of load at a certain movement

rt, Rt

Ultimate Toe Resistance does not exist other than as a definition of load at a certain movement

Ultimate Toe Resistance is not

50

100

150

200

AG

E S

HA

FT S

HEA

R(K

Pa)

O-cell to GL3

GL3 to GL1Pile D2000

2,000

3,000

4,000

RA

GE

STR

ESS

AN

DSH

EAR

(K

Pa)

Toe Resistance

Pile D2000

Shaft and toe resistances from full-scale static loading tests on a 2,000 m diameter, 85 m long bored pile in silty clay

Shaft Resistance Toe Resistance

1818

0

50

0 20 40 60 80 100

MOVEMENT (mm)

AVE

R

0

1,000

0 20 40 60 80 100MOVEMENT (mm)

AVE

R S

Shaft resistances(repeated for reference)

The above curve shows the shape of theload-movement every toe resistance."Ultimate Toe Resistance" does not exist!

A pile toe reacts to load by a stiffnessresponse and failure does not occurhowever much the pile toe is moveddown.

3/24/2013

4

Pile capacity is the combined effect of shaft resistance and toe resistance.

Shaft resistance is governed by shear strength, which has an ultimate value. That is, shaft capacity is reality.

In contrast, toe resistance is governed by

1919

In contrast, toe resistance is governed by compression, which does not have an ultimate value. As the load is increased, a larger and larger soil volume is stressed to a level that produces significant compression, but no specific failure or peak value: Toe capacity is a delusion.

Analysis Methods for Determining Shaft Resistance, rs

The Total Stress Method

The Lambda Method

Th SPT M th d

2020

The SPT Method

The CPT and CPTU Methods

The Pressuremeter Method

The Beta Method

where rs = unit shaft resistance

u = undrained shear strength = reduction coefficient for u > 100 KPa

[ ]uusr ==

Piles in Clay

Total Stress Method

"Alpha analysis"

2121

The undrained shear strength can be obtained from unconfined compression tests, field vane shear tests, or, to be fancy, from consolidated, undrained triaxial tests. Or, better, back-calculated from the results of instrumented static loading tests. However, if those tests indicate that the unit shaft resistance is constant with depth in a homogeneous soil, dont trust the analysis!

2222

Clay adhering to extracted piles

Photo courtesy of K.R. Massarsch

The Lambda MethodVijayvergia and Focht (1972)

)2'( mms cr += where rm = mean shaft resistance along the pile

= the lambda correlation coefficientm = mean overburden effective stresscm = mean undrained shear strength

Piles in Clay

2323

Approximate Values of Embedment (Feet) (m) (-)

0 0 0.5010 3 0.3625 7 0.2750 15 0.2275 23 0.17

100 30 0.15200 60 0.12

The Lambda method was developed for long piles in clay deposits (offshore conditions)

{ } 'tan')/2()()(lg87.0)(016.02.28.0 2.042.0 zts bhOCRSOCRr +=where rs = unit shaft resistance

OCR = overconsolidation ratioSt = sensitivity

Piles in Clay

A method from fitting a variety of parameters to results from static loading tests

2424ICP (Imperial College Pile method)

Jardine, Chow, Overy, and Standing (2005 )

h = height of point above pile toe ; h 4bb = pile diameter = interface friction angle

3/24/2013

5

The SPT MethodMeyerhof (1976)

Rs = n N As D

where Rs = ultimate shaft resistance

n = a coefficient

N = average N-index along the pile shaft (taken as a pure number)

Piles in Sand

2525

g g p ( p )

As = unit shaft area; circumferential area

D = embedment depth

n = 2103 for driven piles and 1103 for bored piles (N/m3)[English units: 0.02 for driven piles and 0.01 for bored piles (t/ft3)]

For unit toe resistance, Meyerhof's method applies the N-index at the pile toe times a toe coefficient = 400103 for driven piles and 120103 for bored piles (N/m3)

[English units: 4 for driven piles and 1 for bored piles (t/ft3)]

CPT and CPTU Methods

for Calculating the Ultimate

Resistance (Capacity) of a Pile

Schmertmann and Nottingham (1975 and 1978)

2626

deRuiter and Beringen (1979)

Meyerhof (1976)

LCPC, Bustamante and Gianeselli (1982 )

ICP, Jardine, Chow, Overy, and Standing (2005)

Eslami and Fellenius (1997 )

caOCRt qCr =The CPT and CPTU Methods

where rt = pile unit toe resistance (NK = a dimensionless coefficient, ranging from 15

through 20, reflecting local experience = adhesion factor equal to 1.0 and 0.5 for

normally consolidated and overconsolidatedclays, respectively

An upper limit of 15 MPa is imposed for rt

k

cu N

qS =Stress method

LCPC Bustamante and Gianeselli (1982 )

cs qKr =cat qCr =

3030

C = toe coefficient ranging from 0.40 through 0.55qca = cone stress averaged in a zone 1.5 b above and

1.5 b below the pile toe plus filtering

rt = pile unit toe resistance < 15 KPa,

3/24/2013

6

Soil Type Cone Stress Bored Piles Driven Piles Maximum rtCLCPC CLCPC

(MPa) (- - -) (- - -) (MPa)

CLAY - - qc < 1 0.04 0.50 15

Coefficients and Limits of Unit Toe Resistance in the LCPC Method Quoted from the CFEM (1992)

3131

c

1 < qc < 5 0.35 0.45 15

5 < qc - - - 0.45 0.55 15

SAND - - - qc < 15 0.40 0.50 15

12 < qc - - - 0.30 0.40 15

Soil Type Cone Stress Concrete Piles Steel Piles Maximum rs(MPa) & Bored Piles

KLCPC KLCPC J

(- - -) (- - -) (KPa)

CLAY - - qc < 1 0.011 (1/90) 0.033 (=1/30) 15

1 5 0 025 (1/40) 0 011 ( 1/80) 35

Coefficients and Limits of Unit Shaft Resistance in the LCPC Method Quoted from the CFEM (1992)

3232

1 < qc < 5 0.025 (1/40) 0.011 (=1/80) 35

5 < qc - - - 0.017 (1/60) 0.008 (=1/120) 35

SAND - - - qc < 5 0.017 (1/60) 0.008 (=1/120) 35

5 < qc < 12 0.010 (1/100) 0.005 (=1/200) 80

12 < qc - - - 0.007 (1/150) 0.005 (=1/200) 120

The values in the parentheses are the inverse of the KLCPC-coefficient

cac

t qdbr )5.01( =

cJs qKr = ' b

ICP (Imperial College Pile method)Jardine, Chow, Overy, and Standing (2005 )

3333

tan)')()'(0145.0( 38.013.0 m

tr

zcJ h

bqK +=

bq

qqrz

rzccmc 01.0)]

'(10216.1)'(00125.00203.0(2[' 1

265.0 +=

Egtt qCr =Eslami and Fellenius

(1997 )

Ess qCr =rt = pile unit toe resistance

Ct = toe correlation coefficient (toe adjustment factor)equal to unity in most cases

Shaft Correlation Coefficient

Soil Type*) Cs

Soft sensitive soils 8 0 %

bCt 3

1=

bCt

12=

b in metre

b in inch

3434

qEg = geometric average of the cone point resistance over the influence*) zone after correction for pore

pressure on shoulder and adjustment to effective stress rs = pile unit shaft resistanceCs = shaft correlation coefficient, which is a function of soil

type determined from the soil profiling chartqE = cone point resistance after correction for pore pressure

on the cone shoulder and adjustment to effective stress

*) The Influence zone is 8b above and 4b below pile toe

Soft sensitive soils 8.0 %Clay 5.0 %Stiff clay andClay and silt mixture 2.5 %Sandy silt and silt 1.5 %Fine Sand and silty Sand 1.0 %Sand to sandy gravel 0.4 %

*) determined directly from the CPTU soil profiling

Unit shaft resistance as a function of cone stress, qc in Sandaccording to the LCPC method and compared to the Eslami-Fellenius method

100

120

140

ce, r

s (K

Pa)

Sandy Silt to silty Sand to sandy Gravel

Concrete

Range for the Eslami Fellenius method

3535

0

20

40

60

80

0 5 10 15 20 25 30 35 40

Cone Stress, qc (MPa)

Uni

t Sha

ft R

esis

tan piles

Steel piles

PILES IN SAND

Cone Stress, qc and qt (MPa)

Pile Capacity or, rather, Load-Transfer follows

principles of effective stress

3636

principles of effective stress and is best analyzed using the

Beta method

3/24/2013

7

the Beta method

Unit Shaft Resistance, rs zs

r '=where c = effective cohesion intercept

= Bjerrum-Burland coefficient'z = effective overburden stress

Effective Stress Analysis (Beta-analysis as opposed to Alpha analysis)

3737

dzcAdzrAR zssss )''( +==Total Shaft Resistance, Rswhere As = circumferential area of the pile at Depth z

(surface area over a unit length of the pile)

Shaft Resistance in Sand and in Clay

KMr ''tan =

vsr '=

3838

where rs = unit shaft resistance

M = tan / tan Ks = earth stress ratio = h / vv = effective overburden stress

vss KMr tan =

Approximate Range of Beta-coefficients

SOIL TYPE Phi Beta

Clay 25 - 30 0.20 - 0.35

Silt 28 - 34 0.25 - 0.50

Sand 32 - 40 0.30 - 0.90

Gravel 35 - 45 0.35 - 0.80

0.05 - 0.80 !

3939

Gravel 35 45 0.35 0.80

These ranges are typical values found in some cases. In any given case,actual values may deviate considerably from those in the table.

Practice is to apply different values to driven as opposed to bored piles, but ....

2.0

3.0

4.0

5.0

6.0

coef

ficie

nt i

n s

and

G

Trend line

4040

0.0

1.0

0 5 10 15 20 25 30

LENGTH IN SOIL (m)

-c

HK GEO (2005)CFEM (1992)

Gregersen et al. 1973

Beta-coefficient versus embedment length for piles in sand (Data from Rollins et al. 2005). Ranges suggested by CFEM (1993), Gregersen et al 1973, and Hong Kong Geo (2005) have been added.

1.00

1.50

2.00

2.50

OEF

FIC

IEN

T IN

SA

ND

Concrete piles

Open-toe pipe piles

Closed-toe pipe piles

Gregersen

4141

0.00

0.50

0 50 100 150 200 250 300 350

AVERAGE EFFECTIVE STRESS, 'z (KPa)

-C

O et al. 1973

Beta-coefficient versus average for piles in sand. (Data from Clausen et al. 2005).

1.00

1.50

2.00

2.50

FIC

IEN

T IN

SA

ND

Concrete piles

Open-toe pipe piles

Closed-toe pipe piles

4242

0.00

0.50

0.0 0.2 0.4 0.6 0.8 1.0 1.2

AVERAGE DENSITY INDEX, I D

-C

OEF

Beta-coefficient versus average ID for piles in sand. (Data from Karlsrud et al. 2005).

3/24/2013

8

0.20

0.30

0.40

0.50

0.60co

effic

ient

in

cla

y

Norway Japan Thailand Vancouver Alberta

4343

0.00

0.10

0 20 40 60 80

PLASTICITY INDEX, I P

-c

Beta-coefficient versus average IP for piles in clay. (Data from Karlsrud et al. 2005 with values added from five case histories).

c

CCI

CKr

vD

C eCe

K

tan'

ln100

10

24

302

=Where K = coefficient of earth stress at rest

I = density index (relative density)

The Beta-coefficient has a certain appeal to the academia it seems. This is what is proposed in a recent issue of the ASCE Journal.

44

ID = density index ( relative density )v = effective overburden stressr = reference stress = 100 KPa = triaxial-compression critical-state

friction angleC1 = a coefficient: 0.6< C1

3/24/2013

9

0

1

2

0 50 100 150

UNIT SHAFT RESISTANCE (KPa)

0

1

2

0 100 200 300 400 500 600 700 800

TOTAL SHAFT RESISTANCE (KN)

Pile CCPT-3

Calculations of unit and total shaft resistances for a pile driven into asaprolite (residual soil) in Porto, Portugal. The soil can be classified bothas a clay type and sand type.

Shaft resistance by CPT-methods

4949

3

4

5

6

DEP

TH (

m)

DutchSand

MeyerhofSand

LCPCSand

LCPCClay SchmertmannClay

Eslami-Fellenius

SchmertmannSand

DutchClay

TumayClaya

3

4

5

6

DEPT

H (

m)

Effective StressBeta = 1.00

DutchSand

MeyerhofSand

LCPCClay &Sand

SchmertmannClay

Eslami-Fellenius

SchmertmannSand

DutchClay

TumayClayb

0

1

2

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000

CALCULATED PILE RESISTANCE (KN)

TumayClay

Eslami-Fellenius

SchmertmannClayDutch

Clay

LCPC

DutchSand

MeyerhofSand

Pile CCPT-3

Total resistance by CPT-methods

5050

3

4

5

6

DEP

TH (

m) Schmertmann

Sand

LCPCSand

LCPCClay

a

Lets look at a few case studies

Annacis/Lulu Island Tests, Vancouver,

BC

by UBC 1985

5151

Static loading tests on three 324 mm diameter pipe piles driven to depths of 14 m, 17 m, and 31 m into the Fraser River deltaic soils

0

5

10

15

20

0 5 10 15Cone Stress, qt (MPa)

PTH

(m

)

0

5

10

15

20

0 100 200

Sleeve Friction (KPa)

TH (

m)

0

5

10

15

20

0 500 1,000

Pore Pressure (KPa)

PTH

(m

)

0

5

10

15

20

0 1 2 3 4 5

Friction Ratio (%)

PTH

(m

)

PILES1 2 3 4

PROFILE

Eslami-Fellenius Robertson

CLAY CLAY

SANDSAND

SANDGRAVEL & SAND

CPT and CPTU analysis for capacity

5252

25

30

35

40

DEP

25

30

35

40

DEP

25

30

35

40D

EP

25

30

35

40

DEP

CLAY andSilty

CLAY

CLAY andSilty

CLAY

Annacis/Lulu Island Tests by UBC 1985

The results of the load-movement curves from all three tests combined in

600

800

1,000

1,200

OA

D (K

N)

Depth 16.8 mSet-up Time

85 days

Depth 31.1 mSet-up Time

38 days

5353Data from Lulu Island Tests

by UBC 1985

tests combined in one graph. (With offset limit lines and maximum load in the tests).

0

200

400

0 10 20 30 40

MOVEMENT (mm)

LO

Depth 13.7 mSet-up Time

197 days

Results of CPT and CPTU analysis compared tocapacity from the static loading tests

0

5

10

0 500 1,000 1,500 2,000

SHAFT RESISTANCE (KN)

Eslami-Fellenius

DutchLCPC

SchmertmannUniPile eff.stress

= 0 15

0

5

10

0 500 1,000 1,500 2,000

SHAFT and TOE RESISTANCEs (KN)

Eslami-FelleniusDutchLCPCSchmertmannUniPile eff. stressPile static tests

= 0.15

5454UniPile eff.stress is effective stress analysis matched to results of static tests

15

20

25

30

35

DEP

TH (

m)

= 0.15

= 0.20

= 0.15

15

20

25

30

35

DEP

TH (

m)

0.15 Nt = 7

= 0.20 Nt = 25

= 0.15 Nt = 3

Test too soon after EOID

3/24/2013

10

150

a)

O-cell to GL3 GL3 to GL2 GL2 to GL1O-cell to GL2 O-cell to GL1

Sunrise City Project, HoChiMinh City, Vietnam1,800 mm diameter bored piles constructed to 70 m depthUnit shaft resistances versus measured downward movement at depths of 50 m

150

Pa)

O-cell to GL4 GL4 to GL3 GL3 to GL2O-cell to GL3 O-cell to GL2 O-cell to GL1

SHAFT RESISTANCE

HoChiMinh

Ha Noi

Cai Mep Port

55

0

25

50

75

100

125

0 1 2 3 4 5 6 7 8 9 10

MOVEMENT (mm)

UN

IT S

HA

FT R

ESIS

TAN

CE

(KPa

TBP-1

Next reading was at 56 mm

= 0.14

0

25

50

75

100

125

0 1 2 3 4 5 6 7 8 9 10

MOVEMENT (mm)

UN

IT S

HA

FT R

ESI

STA

NC

E (K

P

TBP-2

= 0.13

Next reading was at 35 mm

No records were obtained during the sudden movement occurring at about 5 mm

0

500

1,000

1,500

2,000

2,500

0 50 100 150 200

MOVEMENT (mm)

UN

IT R

ESIS

TAN

CE

(KPa

)

TBP-1

Unit Toe Resistance

Unit Shaft Resistances

10% of diameter

TOE RESISTANCE

56

0

500

1,000

1,500

2,000

2,500

0 50 100 150 200

MOVEMENT (mm)

UN

IT R

ESIS

TAN

CE

(K

Pa)

TBP-2

TBP-1Unit Toe Resistance

Unit Shaft Resistances

The stiffness of the toe stress-movement is unusually soft for adense sand and typical of a pilehaving a layer of debris at the bottomof the shaft when the concrete wasplaced. A pile a few metre to the sidewas constructed using the samemethod and equipped with a coringtube. Coring through this pile toe intothe soil two weeks after constructionrevealed presence of about 30 mm ofsoft material between the pile and thesoil.

Core from the pile toe and into the soil below

57

Bridge over Panama Canal, Paraiso Reach, Republic of PanamaO-cell test on a 2.0 m (80 inches) diameter, 30 m (100 ft) deep shaft

drilled into the Pedro Miguel and Cucaracha formations, February 2003.

0

5

0 5,000 10,000 15,000 20,000 25,000 30,000

LOAD (KN)

0.30

0.45

5858

10

15

20

25

30

DEP

TH (

m) 0.30

___

1.20

O-cell Tests on an 11 m long, 460 mm square precast concrete pile driven in silica sand in

North-East Florida(Data from McVay et al 1999)

0

2

4

6

8

0 500 1,000 1,500 2,000 2,500 3,000

Shaft Resistance, Rs (KN)

(m

)

E-FLCPCSchmertmannDutchMeyerhofBetaTests

5959

(Data from McVay et al. 1999)

A study of Toe and Shaft Resistance

Response to Loading

10

12

14

16

18

20

DEP

TH

The foregoing analysis results are quite good predictions

They were performed after the test results were known

Such predictions are always the best!

So, what about true predictions?

6060

Lets see the results of a couple ofPrediction Events

p

3/24/2013

11

ULTIMATE R

Prediction Event at Deep Foundations Institute Conference in Raleigh, 1988

6161

44 ft embedment, 12.5 inch square precast concrete driven through compact silt and into dense sand

Capacity in Static Loading Test = 200 tonsRESISTANCE

TonsPREDICTORS (60 individuals)

1,500

2,000

2,500

ity (

KN

)

Orlando 2002 Predictions

Max LoadAvailable

6262

0

500

1,000

Predictors

Cap

ac

500

600

700

KN

)

0 20 40 60 80MOVEMENT (mm)

FHWA Washington, DC, 1986

273 mm diam. closed-toe pipe pile driven 9.1 m into hydraulic sand fill

6363

0

100

200

300

400

1 2 3 4 5 6 7 8 9 10PREDICTIONS

CA

PAC

ITY

( 800

1,000

1,200K

N)

0 2 4 6 8 10 12 14 16 18MOVEMENT (mm)

FHWA Baltimore, MD, 1980

Two 273 mm diam. closed-toe pipe piles driven 13.1 m into Beaumont clay

6464

0

200

400

600

800

PARTICIPANTS

CA

PAC

ITY

(K

1,500

2,000

2,500

3,000

3,500

OA

D (

KN

)

Singapore 2002

1,400

1,600

1,800

2,000

65

0

500

1,000

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33

L

400 mm H-Pile (168 kg/m) driven through sandy clay to a 15 m embedment

0

200

400

600

800

1,000

1,200

0 10 20 30 40 50MOVEMENT (mm)

LOA

D (

KN

)

Brazil 2004: Bored pile (Omega screw pile) 23 m long, 310 mm diameter

0

2

4

6

8

0 20 40 60 80

Water Content (%)

(m)

0

5

10

0 5 10 15 20 25N-Index (blows/0.3)

(m)

SPT 18at 23 m Pile

0

2

4

6

8

0 25 50 75 100

Grain Size (%)

(m)

SILT

SAND CLAY

Sandy SiltyCLAY (Laterite)

Sandy SILT

6666

10

12

14

16

18

20

DEP

TH

wnwP wLGW

15

20

25

DEP

TH

10

12

14

16

18

20

DEP

TH Sandy SILT

and CLAY

Sandy ClayeySILTGW

3/24/2013

12

Brazil 2004

Static Loading Test

on a 23 m 310 mm bored pile

Load-Movement Response

1,500

2,000

2,500

KN

)

Prediction Compilation

2,000

2,500PUSH L= 23m

0 5 10 15 20 25 30

MOVEMENT (mm)

6767

0

500

1,000

0 10 20 30 40

MOVEMENT (mm)

LOA

D (

K

0

500

1,000

1,500

PARTICIPANTS

LOA

D (

KN

)

Portugal 2004. Precast 350 mm diameter pile driven to 6 m depthin a saprolite, a residual soil consisting of silty clayey sand.

0

1

2

3

0 10 20Cone Stress, qt (MPa)

) 1 500

2,000

2,500

3,000

PAC

ITY

(KN

)

CAPACITY FROM STATIC LOADING TEST

Pile C1

6868

4

5

6

7

8

DEP

TH (

m

0

500

1,000

1,500

1PREDICTIONS

TOTA

L C

AP

0

OFFSET LIMIT LOAD

1,200

1,400

1,600

1,800

KN

)

Pipe-Pile

0 10 20 30 40MOVEMENT (mm)

Northwestern University, Evanston, Illinois, 1989.15 m embedment, 457 mm diameter closed-toe pipe piles driven in sand on clay.

6969

0

200

400

600

800

1,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

CA

PAC

ITY

(K

PREDICTIONS

Finno 1989

Edmonton, Alberta, 2011

Prediction of load-movement and capacity of a 400-mm diameter, 18 mlong, augercast pile constructed in transported and re-deposited glacial till.

2 000

3,000

4,000D

(KN

)E = 20 GPaE = 35 GPa

70

0

1,000

2,000

0 5 10 15 20 25 30 35 40 45 50

MOVEMENT (mm)

LOA

D

10 capacity predictions are at movements > 50 mm

7 mm (4 mm + b/120 mm)TEST RESULTS

Values

Rea

ltive

Fre

quen

cy

2

= Standard Deviation, = 833 = Mean, 1,923 / = Coefficient of Variation, COV = 0.43

Mean,

4

NORMAL DISTRIBUTIONEdmonton 2011

71

CAPACITY PREDICTIONS

T he area between - and + f ro m the mean value is 68% o f to tal areaT he area between -2 and +2 f ro m the mean value is 95% o f to tal areaT he area between -3 and +3 f ro m the mean value is 99% o f to tal area

0

100

200

0 10 20 30 40 50 60 70 80 90 100

PRED

ICTE

D L

OA

D =

100

MOVEMENT (mm)

NORMALIZED TO LOAD

Forthcoming Prediction Event in Bolivia April 2013

Four bored instrumented piles in sand tested in compression

0

5

2.9 m GW1.0 m

4.5 m

1.0 m

4.5 m

Groundsurface

TP1 TP2 TP3 TP4 "Std" FDP FDP "Std" +EB +O-cell +EB BH1 BH3 BH 4 BH2

0.0 m 400 mm 440 mm 400 mm 400 mm

72

5

10

15

20

25

DE

PTH

(m

)

1.2 m17.5 m 2.5 m

15.0 m

O-cell

EB EB

600 mm

5

7.5 m

10.5 m

13.5 m

16.5 m 15.8 m

4.5 m

7.5 m

10.5 m

13.5 m

Test Pile Configurations and Strain-Gage Levels

440 mm400 mm 600 mm

3/24/2013

13

0

2

4

6

8

10

0 10 20 30 40 50N (blows/0.3m)

PTH

(m

)

SPT1SPT2SPT3

0

2

4

6

8

10

0 5 10 15 20 25 30

WATER CONTENT (%)

TH (

m)

0

2

4

6

8

10

0 20 40 60 80 100

GRAIN SIZE (%)

TH (

m)

Fine to Medium Sand

Medium to Coarse SandFines

BH-1

Soil Profile

73

12

14

16

18

20

DEP

10

12

14

16

18

20

DEP

T 10

12

14

16

18

20

DEP

T Gravel

Zone of Clay and Clayey Sand (no samples)

Deadline for submitting a prediction is April 1I will be glad to email the details for how to submit one.

Pore Pressure Dissipation

0

5

10

0 100 200 300 400 500 600

PORE PRESSURE (KPa)

(m)

0

5

10

0 100 200 300 400 500 600

PORE PRESSURE (KPa)

(m)

0

5

10

0 100 200 300 400 500 600

PORE PRESSURE (KPa)

(m)

7474Paddle River, Alberta, Canada (Fellenius 2008)

15

20

25

DEP

TH

Before Driving

EOID

Total Stress

15

20

25

DEP

TH

30 Days after EOID 15 Days

after EOID

Before Driving

EOID

Total Stress

15

20

25

DEP

TH

4 Years after Driving

30 Days after EOID 15 Days

after EOID

Before Driving

EOID

Total Stress

800

1,000

1,200

1,400

1,600

D (

KN

)

Effective Stress Analysis

0

5

10

0 500 1,000 1,500 2,000

LOAD (KN)

(m)

4 Years after EOID

7575

0

200

400

600

0 10 20 30 40 50

MOVEMENT (mm)

LOA

Paddle River, Alberta, Canada

15

20

25

DEP

TH (

15 Days after EOID

30 Days after EOID

All three analyses apply the same coefficients coupled with the actual

pore pressure distribution

If we want to know the load distribution, we can measure it. But, what we measure is the increase of load in the pile due to the load applied to the pile head. What about the load in the pile that was there before

76

pwe started the test?

That is, the Residual load.

Normalized Applied Load

Load distributions in

static loading tests on

four instrumented

77

D E P T H

piles in clayS d

Example from Gregersen et al., 1973

0

2

4

6

8

0 50 100 150 200 250 300

LOAD (KN)

(m)

0

2

4

6

8

0 100 200 300 400 500 600

LOAD (KN)

(m) True

Residual

True minus Residual

78

B. Load and resistance in DA

for the ultimate load applied

Sand810

12

14

16

18

DE

PTH

(

Pile DA

Pile BC, Tapered

8

10

12

14

16

18

DE

PTH

(

A. Distribution of residual load in DA and BC

before start of the loading test

3/24/2013

14

FHWA tests on 0.9 m diameter bored pilesOne in sand and one in clay

(Baker et al., 1990 and Briaud et al., 2000)

0

2

4

0 10 20 30 40

Cone Stress and SPT N-Index(MPa and bl/0.3 m)

Silty Sand

0

2

4

0 10 20 30 40

Cone Stress (MPa)

ClaySilty

Sand Clay

79

6

8

10

12

DEPT

H (m

)

Sand

Pile 4

6

8

10

12

DEPT

H (m

)

Pile 7

N

qc Sand Clay

ANALYSIS RESULTS: Load-transfer curves

0.0

2.0

4.0

0 1,000 2,000 3,000 4,000 5,000

LOAD (KN)

m)

0.0

2.0

4.0

0 1,000 2,000 3,000 4,000 5,000

LOAD (KN)

)

True Distribution

0.0

2.0

4.0

0 1,000 2,000 3,000 4,000 5,000

LOAD (KN)

m)

Measured Distribution

0.0

2.0

4.0

0 1,000 2,000 3,000 4,000 5,000

LOAD (KN)

m)

True Distribution

Residual Load

80

6.0

8.0

10.0

12.0

DEP

TH (

m

PILE 4SAND

Measured Distribution6.0

8.0

10.0

12.0

DEP

TH (

m)

PILE 4SAND

Residual Load

Measured Distribution

6.0

8.0

10.0

12.0

DEP

TH (

m

PILE 7CLAY

6.0

8.0

10.0

12.0

DEP

TH (

m

PILE 7CLAY

Results of analysis of a Monotube pile in sand(Fellenius et al., 2000)

0

5

0 1,000 2,000 3,000

LOAD (KN)

Measured Resistance

Residual Load

81

10

15

20

25

DE

PTH

(m

)

True Resistance

Method for evaluating the residual load distribution

0

2

4

0 500 1,000 1,500 2,000

RESISTANCE (KN)

Measured Load

Shaft

82

6

8

10

12

14

16

DE

PTH

(m

)

Measured Shaft ResistanceDivided by 2

Residual Load

True Resistance

ExtrapolatedTrue Resistance

Resistance

0

5

10

15

20

0 500 1,000 1,500 2,000 2,500LOAD (KN)

(m)

Static Loading Testat Pend Oreille, Sandpoint, Idaho, for

the realignment of US95

406 m diameter,45 m long, closed-toe pipe pile

driven in soft clay

Determining True Resistancefrom Measured Resistance (False Resistance)

Cl

83

25

30

35

40

45

50

DEP

TH (

Fellenius et al. (2004)

driven in soft clay

200+ m

Clay

0

5

10

15

20

-500 0 500 1,000 1,500 2,000

LOAD (KN)

(m)

= 0.60

= 0.06

AS MEASURED,i.e. "FALSE RES."

A

= 0.09

0

5

10

15

20

-500 0 500 1,000 1,500 2,000

LOAD (KN)

(m)

= 0.60

= 0.09

= 0.09

AS MEASURED,i.e. "FALSE RES."

CPTu Eslami-Fellenius

B

84

Test on a strain-gage instrumented, 406 mm diameter,45 m long pile driven in soft clay in Sandpoint, Idaho

25

30

35

40

45

50

DE

PTH

= 0.06

"TRUE RES." RESIDUAL LOAD

AFTER 1st UNLOADING

25

30

35

40

45

50

DE

PTH

= 0.10

"TRUE RES." per CPTu

RESIDUAL LOAD

AFTER 1st UNLOADING

= 0.10

Extrapolated

3/24/2013

15

0

5

10

15

0 500 1,000 1,500 2,000 2,500 3,000 3,500

LOAD (KN)

PTH

(m

)

True Resistance

HEAD-DOWN AND FULL RESIDUAL LOAD

Residual Load

True Resistance

False Resistance

Silty Sand

Silty Clay

0

5

10

15

0 500 1,000 1,500 2,000 2,500 3,000 3,500

LOAD (KN)

PTH

(m

)

HEAD-DOWN AND PARTIAL RESIDUAL LOAD

True

False Resistance

Shaft Resistance

Typical Example: Table 7.3 in the Red Book

85

20

25

30

35

DE

P Resistance

Residual and TrueToe Resistance

Transition Zone

Silty Sand

Glacial Till

20

25

30

35

DEP

Residual Load

Resistance

Residual and TrueToe Resistance

Transition Zone

Resistance

The effect of residual load on an uplift test

0

5

10

-2,000 -1,500 -1,000 -500 0 500 1,000

LOAD (KN)

m)

True Resistance

TENSION TESTAND FULL RESIDUAL LOAD

Residual Load

0

5

10

-2,000 -1,500 -1,000 -500 0 500 1,000

LOAD (KN)

m)

Residual Load

True Resistance

TENSION TESTAND PARTIAL RESIDUAL LOAD

8686

15

20

25

30

35

DE

PTH

(m

False Resistance

Toe Resistancein an Uplift Test?!

15

20

25

30

35

DEP

TH (

m

False Resistance

Toe Resistancein an Uplift Test?

Combining the results of a head-down test with those of a tensions test will help determining the true resistance

0

5

10

15

0 500 1,000 1,500 2,000 2,500 3,000 3,500

LOAD (KN)

H (

m)

HEAD-DOWN AND PARTIAL RESIDUAL LOAD

FalseHead-down

True Shaft

False TensionTest

8787

20

25

30

35

DEP

TH

Residual Load

True Resistance

Residual and TrueToe Resistance

Transition Zone

True Shaft Resistance

Not directly useful below this level

Now you know why some claim that resistance in tension is smaller than that in compression

400

600

800

1,000

LOA

D (

KN

)

No Residual Load

Residual Load present

No Strain Softening

Presence of residual load is not just of academic interest

400

600

800

1,000

LOA

D (

KN

)

With Strain Softening

Residual Load present

No Residual Load

8888

0

200

400

0 5 10 15 20 25 30

MOVEMENT (mm)

L

OFFSET LIMIT LOAD

0

200

400

0 5 10 15 20 25 30

MOVEMENT (mm)

L

OFFSET LIMIT LOAD

"Residual Load " follows the same principle and mechanism as "Drag Load". The distinction made is that by residual load we mean the locked-in load present in the pile immediately before we start a static loading test. By drag load we mean the load present in the pile in the long-term.

Additional Comments on Residual load

8989

Residual load as well as drag load can develop in coarse-grained soil just as it does in clay soil.

Both residual load and drag load develop at very small movements between the pile and the

soil.